The present invention relates to an image display system that modulates illumination light from a light source and displays two-dimensional images. More particularly, this invention relates to an image display system implemented with a spatial light modulator which modulates incoming light by opening and closing micro-windows configured as a two dimensional pixel array.
After the dominance of cathode ray tube (CRT) technology in the display industry over the past 100 years, the Flat Panel Display (FPD) and Projection Display technologies are now gaining popularity because of a smaller form-factor of the display control system while projection and display of images of greater size onto a bigger display screen can be more conveniently performed. Among several types of projection display systems, projection display systems using micro-display are gaining consumers' recognition because of high performance of picture quality as well as lower cost than the display systems implemented with FPDs. There are two types of micro-display technologies implemented in the projection display systems now made available in the market. The first type of display system is the micro-LCD (Liquid Crystal Display) system and the other type display system is the display system that implements the micromirror technology. The images displayed from a micromirror device have a significant advantage because of higher brightness by displaying the images by projecting an un-polarized light over the display image projected from a micro-LCD system, which uses polarized light.
More specifically, the electromechanical mirror device is drawing a considerable interest as a spatial light modulator (SLM). Micromirror devices have substantial advantages over LCD systems, because they do not use polarized light as LCD and creating polarized light causes substantial loss of incoming light nearly 50%. Furthermore, the micromirror devices also have substantial faster response time than LCD and this faster speed enables Color Sequential Control, meaning using a single device and alternating colors as fast as viewers do not recognize the change of colors.
Additionally, due to the slow speed, the LCD image projection systems typically are required to implement three panels and do not allow for Color Sequential Control. Compared with systems implemented with three panels, the image display systems implemented with a single panel has significant cost advantages of providing with device with a much lower cost than the three panel systems.
Even though the micromirror devices have significant advantages over the LCD systems, the optics systems are usually more complicated because of reflection systems rather than transmissive systems. Reflective optical systems often require larger sizes than transmissive optical system. The advantages and cost benefits of the micromirror devices are adversely affected due to this requirement of a larger optical system when the reflective optical configuration is implemented. In addition to the requirement of optics of larger size, the reflective display devices are further limited to application in the projection display apparatuses while the transmissive display systems have broader applications for implementation in the direct view and projection display systems, such as the LCD display systems.
U.S. Pat. Nos. 7,417,782 and 7,460,290 disclose MEMS Shutters such as that shown in FIG. 15A, with shutters employ the sliding shutter to open and shut off a shutter manufactured by the MEMS technology. However, such systems are limited by the fact that the structure cannot have more than 50% of opening due to its sliding door type structure. In contrast, the Micro-windows can achieve higher brightness and are more desirable because the micro-windows have higher opening ratio.
The technical article, “Magneto-structural Simulation of a MEMS Micro-shutter” by Abed M. Khaskia published at FEMCI Workshop/NASA GSFC on Jun. 15, 2004, shows that micro-shutter with torsion hinge actuated by magnetic force. However, this structure as that shown in FIG. 15B, requires high power to drive.
Therefore, a need still exists in the art of image display projection systems. More particularly in the micromirror device display system to provide a new and improved optical configuration and design methods to simplify the optical transmission configurations and reduce the size of the spatial light modulator (SLM) such that the difficulties and limitations as now encountered by those of ordinary skill in the art can be resolved. Another need exists to improve the brightness and resolution of direct view LCD display systems whose light utilization is below 10% and requires three color dots in a pixel.